The current market for modern passenger aircraft intended for use in commercial aviation is highly competitive and necessitates that strict attention be paid to certain industry specific design requirements, such as passenger comfort. For example, passenger planes are being designed for “Best-In-Class” passenger comfort, and this includes cabin noise level goals that are as low as or lower than any current large commercial aviation aircraft.
In such aircraft, the airplane fuselage sidewalls in general, and the passenger windows in particular, are the dominant paths of external noise entry. This is of primary concern on modern passenger planes having larger passenger windows and composite fuselages, both of which may transmit external noise. The predominant sources of noise that transmit through the “window belt,” i.e., the rectangular areas on opposite sides of the aircraft's fuselage that include the laterally facing passenger windows, and may number as many as 52 windows per side, include turbulent aerodynamic flow along the fuselage, as well as noise originating in the exhaust plume of the aircraft's engines. Both sources have large low-frequency components that are difficult to reduce without adding significant weight to the structure. As weight is an additional critical consideration for the performance of the airplane, any weight-reduction concepts are necessarily of very high value. Thus, a window design that reduces the area of fuselage skin in the window belt above and below the window transparencies is highly desirable. Besides weight limitations, the need to use optically transparent materials in the windows further complicates window noise control efforts.
Thus, an important need exists in the aviation industry for a window design for a subsonic passenger aircraft that is optimized to provide maximum passenger exterior visibility while minimizing the amount of acoustic noise transmitted through the windows to the interior of the aircraft during flight.